1. Field of the Invention
The present invention relates to a hand position detecting device and a hand position control method which detects rotational positions of seconds, center and hour hands.
2. Description of the Related Art
Conventionally, a hand position detecting device which detects the rotational positions of hands of a timepiece is known, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-162336.
The hand position detecting device comprises a first drive system in which a first drive motor transmits its rotation to a seconds wheel which in turn causes a seconds hand to sweep around a dial, a second drive system in which a second drive motor transmits its rotations to the center and hour wheels to cause the center and hour hands, respectively, to sweep around the dial. The hand position detecting device also comprises a photosensor including a light emission element and a photo detection element. The photosensor optically detects a first, a second and a third light-passing apertures provided respectively in the seconds, center and hour wheels with the aid of the light emission element and the photo detection element when the seconds, center and hour wheels of the first and second drive systems rotate after pointing to the same direct on on the same axis. The hand position detecting device detects respective rotational positions of the seconds, center and hour wheels based on detected signals from the photosensor and hence rotational positions of the seconds, center and hour hands are determined.
However, the conventional hand detecting device only determines the rotational positions of the seconds, center and hour hands. Thus, when it is determined that these hands rotate around the dial correctly, normal rotations are continued. However, when the hand detecting device is left in darkness for long periods, detection of the hands is repeated many times, thereby consuming a significant amount of battery power.